Magnetic domain storage devices are known in the prior art, where the direction of magnetization or polarity within a domain is utilized to indicate information stored in the domain. Domain walls, formed between domains of opposed polarity, have also been utilized in conjunction with domains for storage purposes. In these devices, the entire domain wall is made to be of a single uniform polarity, and can be used in conjunction with the domains for data storage. Such domain-domain wall devices are described for example in U.S. Pat. Nos. 3,140,471, 3,114,898, and 3,176,276.
Since as a generality there is one domain wall for each domain, using the walls or domains results in equal storage capacity. Using both merely doubles storage capacity. As domain or wall storage is non-volatile, inexpensive, and has no moving parts in some configurations, it is a desirable storage medium. Higher density storage is still more desirable utilizing the domain concept.
Thus, an object of this invention is to significantly increase storage capacity in domain-domain wall devices by storing a plurality of data bits in a single wall.
Another object is to optionally represent data either by the presence and absence of wall polarity reversals or by the sense of such reversals as desired.
Still another object is to afford means for accessing data in a non-mechanical manner by utilizing equilibrium domain configurations that are translated under the influence of externally applied fields.
The overall object is to provide a storage medium, method and apparatus utilizing wall polarity reversal as a high density storage means.
These and other objects will best be understood in relation to the summary, drawings, and general description that follows.